Paints typically contain four essential ingredients: carrier liquid, binder, pigment, and additives. Each of such ingredients may comprise a single component or several different items mixed into the paint.
The carrier liquid is a fluid component of the paint which serves to carry all of the other paint components. The carrier liquid is part of the wet paint and usually evaporates as the paint forms a film and dries on a surface. In latex paints, the carrier liquid is usually water. In oil-based paints, the carrier liquid is usually an organic solvent. The amount and type of liquid is usually determined by features of the other paint components.
The binder component of a paint is what causes the paint to form a film on and adhere to a surface. In a latex paint, the binder comprises a latex resin, usually selected from acrylics, vinyl acrylics, or styrene acrylics. In a latex paint, the latex resin particles usually are in a dispersion with water as the carrier liquid.
Pigments provide the paint with both decorative and protective features. Pigments are solid particles used to provide the paint with various qualities, including but not limited to color, opacity, and durability. The paint may also contain other solid particles such as polyurethane beads or other solids. Pigments and other solids add bulk to the paint and their levels are related to the gloss or flatness of the paint.
A multitude of additives may be included in paints. The additives are typically used at relatively low levels in the paint formulation, but contribute to various properties of paints, including rheology, stability, paint performance, and application quality.
Biocides, or specifically, antibacterial agents, are additives which have bacteriostatic and bactericidal properties. Biocides work to kill bacteria by one or more of several different mechanisms, including but not limited to interfering with cell wall synthesis, damaging the cell membranes, inhibiting protein synthesis, and interfering with nucleic acid synthesis. Some biocides may also have anti-viral effects, serving to inactivate viruses, such as cold and flu viruses.
A variety of biocidal agents are well known and are used for various purposes. Such biocides include inorganic biocidal agents, for example, those containing metal ions, such as silver, zinc, and copper. Other inorganic biocides include phosphates, metal ion, metal or other biocide containing zeolites or hydroxyapatites. There are also organic biocides including organic acids, phenols, alcohols, and quaternary ammonium compounds.
Quaternary ammonium compounds act as biocides by damaging cell membranes and killing bacteria. This mechanism is likely due to the positive charge on the quaternary ammonium compounds which interact with the negative charge sites of the bacteria.
Quaternary ammonium compounds are not typically added to latex paints, due to a negative effect on the quality of the paint. The prior art has recognized that when added to latex paints, quaternary ammonium compounds cause an undesirable increase in viscosity and cause the polymer and pigments to precipitate. Without being limited to any particular theory, it is believed that the cationic nature of the quaternary ammonium compounds is not compatible with the generally anionic nature of latex paint formulations which results in the precipitation of the components from the dispersion. The precipitation causes the paint to have an undesirable appearance as the precipitate particles cause the dry paint film to have a grainy appearance or texture.